One of the Six Ancestors, she is considered to be the ancestor to all tentacled monsters. She is rumored to be an aggregation of tentacles that assume a human form, and is able to transform, multiply, and divide at will. By creating multiple split bodies, it is possible for her to perform numerous activities at the same time. Her flesh is a predatory organ in of itself, and is capable of capturing and digesting other organisms. She is a self-proclaimed gourmand, but she actually has an incredibly bad diet, and isn't picky about who she greedily preys upon. In addition to humans and monsters, she is said to have voraciously devoured countless angels during the Great Monster Wars, and is known for her brutality. Currently, the one she wants to eat the most is Eden.
In the parallel world known as "Makai" ruled by the Dark God, Hiruko rules over Sabasa. However, Hiruko eroded all of Sabasa, and reduced the city itself into something else entirely. The whereabouts of Sabasa's residents have yet to be confirmed, and it is uncertain what state they are in. Hiruko also plays an important role in the operation of the calamity star weapon [Demiurge]. It is rumored that most of the calamity star is being created from Hiruko's body.
If Hiruko catches a man, she will play around with him before eating him. Her tentacles give complete pleasure to the man as they crawl around his gentials, leading the man to instantly ejaculate just from tasting the finest pleasure. In addition, the man's penis will dissolve while wrapped inside the tentacles, and slowly assimilate with Hiruko's body. The man will experience maddening pleasure and repeatedly climax as his penis is literally melted.